The goal of this master thesis was to optimize the tunnel oxide passivating contact (TOPCon) concept for p-type substrates and implementation in silicon (Si) solar cells. TOPCon and other passivating contacts are believed to be a crucial link for increasing solar cell efficiency and further reducing the costs of photovoltaic (PV) systems. The concept that comes closest to the theoretical Auger limit is the Si heterojunction cell with a record efficiency of 26.6%[1]. A problem with this type of cells is that the process temperature that is allowed is limited, increasing the processing temperature results in decreasing passivation and thus loss of efficiency. The TOPCon concept can withstand higher processing temperatures, which is beneficial when it comes to applying a transparent conductive oxide (TCO) layer of certain metallization schemes. For n-TOPCon good results have been obtained in the past leading to a record efficiency of 25.7%[2]. For p-TOPCon, the efficiency is significantly lower and the cause of this discrepancy is not fully understood yet. In this work, the boron doped TOPCon configuration was optimized by optimizing all of the individual components of this passivating contact concept. During this work the tunnel oxide, which can be grown using variousmethods, proved essential to obtain a good passivation. A comparison was made between four different growth methods for the tunnel oxide, from which it was concluded that the thermally grown tunnel oxide performed best in terms of passivation quality and thermal stability. The optimal p-TOPCon stack was found to consist of three layers: a thin intrinsic hydrogenated amorphous silicon (a-Si:H) layer, followed by a boron doped a-Si:H layer. The p-TOPCon stack is finalized by depositing a thin silicon carbide (SiC) capping layer, which was also boron doped. Besides passivation, the specific contact resistivity was also investigated. A metallization stack consisting of titanium, palladium, and silver proved to result in the lowest contact resistivity values. The lowest value which was measured was 10 m­cm2, this is below the threshold value for which fill factor (FF) losses are to be expected. Implementing a thin tungsten oxide (WOx) layer underneath this metallization stack resulted in a stark increase in the specific contact resistivity values. Furthermore, the tunnel oxide influenced the contact resistivity values, where a lower oxidation time and temperature resulted in lower contact resistivity values. In order to better understand the correlation between contact resistivity and passivation, the contact resistivity values and corresponding recombination current values were fitted to two different models: the oxide tunneling model [3] and the pinholes model [4]. The measured resistivity values all laid in the saturated regime, whichmade it difficult to exclude one of the two models. The passivation quality of the p-TOPCon stack was improved by altering the tunnel oxide to a thermally grown oxide and optimizing the TOPCon stack. This resulted in an implied open-circuit voltage (iVoc) value of 710 mV and an implied fill factor (iFF) value of 84.5 %. A good contact was obtained with a titanium, palladium, silver metallization. This resulted in a specific contact resistivity value of 10m­cm2.